Investigation on Electromagnetic Wave Absorption of SiCw/Si3N4 Composites Exposed to Short-Time Oxidation

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Abstract
As oxidation is inevitable during application of microwave absorbing materials (MAM) exposed to oxygen-containing atmosphere at elevated temperatures. The investigations concerning influences of oxidation on microstructure and microwave absorption (MA) properties are of great significance. Aiming to better regulating MA for Si3N4-based ceramics serviced in high temperature environment, the evolution of MA properties of SiCw/Si3N4 composites (SwSN) after oxidation at 1200 °C in ambient air for short time was studied. It was found that after oxidation for 7.5 h, both the real and imaginary permittivity of SwSN showed only slight decrease due to good oxidation protection provided by dense SiO2 layer formed on the surface. Moreover, SwSN after short-time of oxidation also showed an almost negligible decline in MA properties. SwSN which has good oxidation resistance and stable microwave attenuation abilities was subjected to oxidation at 1200 °C for short time. The results showed its favorable and potential applications in high-temperature microwave absorption fields.